<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
  <head>
    <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
    <title>Retrieved key/data permanence for C/C++</title>
    <link rel="stylesheet" href="gettingStarted.css" type="text/css" />
    <meta name="generator" content="DocBook XSL Stylesheets V1.73.2" />
    <link rel="start" href="index.html" title="Berkeley DB Programmer's Reference Guide" />
    <link rel="up" href="am_misc.html" title="Chapter 4.  Access Method Wrapup" />
    <link rel="prev" href="am_misc_struct.html" title="Storing C/C++ structures/objects" />
    <link rel="next" href="am_misc_error.html" title="Error support" />
  </head>
  <body>
    <div class="navheader">
      <table width="100%" summary="Navigation header">
        <tr>
          <th colspan="3" align="center">Retrieved key/data permanence for C/C++</th>
        </tr>
        <tr>
          <td width="20%" align="left"><a accesskey="p" href="am_misc_struct.html">Prev</a> </td>
          <th width="60%" align="center">Chapter 4. 
		Access Method Wrapup
        </th>
          <td width="20%" align="right"> <a accesskey="n" href="am_misc_error.html">Next</a></td>
        </tr>
      </table>
      <hr />
    </div>
    <div class="sect1" lang="en" xml:lang="en">
      <div class="titlepage">
        <div>
          <div>
            <h2 class="title" style="clear: both"><a id="am_misc_perm"></a>Retrieved key/data permanence for C/C++</h2>
          </div>
        </div>
      </div>
      <p>When using the non-cursor Berkeley DB calls to retrieve key/data items under
the C/C++ APIs (for example, <a href="../api_reference/C/dbget.html" class="olink">DB-&gt;get()</a>), the memory to which the
pointer stored into the <a href="../api_reference/C/dbt.html" class="olink">DBT</a> refers is only valid until the next
call to Berkeley DB using the <a href="../api_reference/C/db.html" class="olink">DB</a> handle.  (This includes <span class="bold"><strong>any</strong></span>
use of the returned <a href="../api_reference/C/db.html" class="olink">DB</a> handle, including by another thread of
control within the process.  For this reason, when multiple threads are
using the returned <a href="../api_reference/C/db.html" class="olink">DB</a> handle concurrently, one of the
<a href="../api_reference/C/dbt.html#dbt_DB_DBT_MALLOC" class="olink">DB_DBT_MALLOC</a>, <a href="../api_reference/C/dbt.html#dbt_DB_DBT_REALLOC" class="olink">DB_DBT_REALLOC</a> or <a href="../api_reference/C/dbt.html#dbt_DB_DBT_USERMEM" class="olink">DB_DBT_USERMEM</a>
flags must be specified with any non-cursor <a href="../api_reference/C/dbt.html" class="olink">DBT</a> used for key or
data retrieval.)</p>
      <p>When using the cursor Berkeley DB calls to retrieve key/data items under the
C/C++ APIs (for example, <a href="../api_reference/C/dbcget.html" class="olink">DBC-&gt;get()</a>), the memory to which the
pointer stored into the <a href="../api_reference/C/dbt.html" class="olink">DBT</a> refers is only valid until the next
call to Berkeley DB using the <a href="../api_reference/C/dbc.html" class="olink">DBC</a> returned by <a href="../api_reference/C/dbcursor.html" class="olink">DB-&gt;cursor()</a>.</p>
    </div>
    <div class="navfooter">
      <hr />
      <table width="100%" summary="Navigation footer">
        <tr>
          <td width="40%" align="left"><a accesskey="p" href="am_misc_struct.html">Prev</a> </td>
          <td width="20%" align="center">
            <a accesskey="u" href="am_misc.html">Up</a>
          </td>
          <td width="40%" align="right"> <a accesskey="n" href="am_misc_error.html">Next</a></td>
        </tr>
        <tr>
          <td width="40%" align="left" valign="top">Storing C/C++ structures/objects </td>
          <td width="20%" align="center">
            <a accesskey="h" href="index.html">Home</a>
          </td>
          <td width="40%" align="right" valign="top"> Error support</td>
        </tr>
      </table>
    </div>
  </body>
</html>
